Ben Affleck’s Batman will be teaming up with a female Robin for his debut as the caped crusader in Warner Bros’ Batman v Superman: Dawn of Justice, according to an anonymous extra on the forthcoming superhero epic.Jena Malone, who recently made an appearance in the Hunger Games fantasy saga as the tempestuous Johanna Mason, is reputedly in line to play Carrie Kelley. The character was introduced in Frank Miller’s seminal 1986 graphic novel The Dark Knight Returns, and has been called the first full-time female version of Batman’s best-known sidekick in the DC Comics title.

The news broke through the WILX-10 News station in Michigan, where Batman v Superman: Dawn of Justice has been filming at the Michigan State University. The extra told reporter Kirk Montgomery: “I’ve also learned that the character of Robin is now female.” Meanwhile, Malone has been spotted on set and at recent film premieres sporting Kelley’s trademark red crop.

Studio Warner Bros has not yet made any public comment on the rumour. However, several US sites are reporting that the extra in question now faces a possible $5m fine for breaking a non-disclosure agreement.Batman v Superman, the followup to Zack Snyder’s 2013 superhero epic Man of Steel, will feature Affleck taking on Henry Cavill’s Superman. The film already looks set to be a crowded affair, with a debut for Gal Gadot’s Wonder Woman and potential bows for Jason Momoa’s Aquaman and Ray Fisher’s Cyborg.

Snyder is said to be riffing heavily on The Dark Knight Returns, which sees an older, jaded Batman coming into conflict with Superman after the latter is called in to take down an increasingly out-of-control dark knight. Kelley is a 13-year-old schoolgirl in the comics, somewhat younger than the 29-year-old Malone.

While the introduction of a new movie Robin would usually prove controversial with fans, the cache of Miller’s classic graphic novel could yet make the character’s big screen debut a popular move. Dawn of Justice is due in cinemas for March 2016.